Output Stages and Power Amplifiers Conduction Angle

Output Stages and Power Amplifiers Conduction Angle

Output stage delivers the output signal

to the load without loss of gain due to

Low output resistance

Example – An Operational Amplifier

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POWER AMPLIFIER

•Common-emitter amplifiers and operational amplifiers require high impedance loads.

•To drive low impedance loads, a power output stage is required.

•Designs vary in complexity, linearity and efficiency.

•Power dissipation and thermal effects must be considered.

Properties of Power Amplifier Stage 

Low voltage gain (usually unity).

High current gain. 

Low output impedance.

R High input impedance

Differences between power amplifier designs

Efficiency / Power dissipation.

Complexity / Cost.

Linearity / Distortion.

Power amplifier designs are usually classified according to their conduction angle.

Conduction Angle

The conduction angle gives the

proportion of an a.c. cycle which the output devices conduct for.

E.g.

On all the time  Þ  360 °

On half the time  Þ  180 °

etc.